Mario Draghi, President of the European Central Bank, addresses the Economic Club of New York at a luncheon in the Manhattan borough of New York December 4, 2015.Lucas Jackson

FRANKFURT (Reuters) - Hints by Mario Draghi ahead of last Thursday's ECB rate meeting that the euro zone may need another big injection of money backfired, stiffening the resolve of more conservative central bankers who criticised him for raising expectations too high, sources familiar with the discussions said.

The European Central Bank President and his chief economist Peter Praet stoked expectations with dovish speeches in the weeks before the meeting but the ECB’s Governing Council concluded that markets needed to be disappointed this time because the economic outlook has improved and new inflation forecasts were not as bad as feared, the sources said.

A pending U.S. Federal Reserve rate hike also factored into the decision, though to a lesser extent, as policymakers were concerned that a big move by the ECB would weaken the euro further and possibly force the Fed to delay its own action on rates to prevent a too rapid divergence of policy between the world’s top two central banks.

The ECB cut its deposit rate on Thursday and extended its monthly asset buys by six months to boost stubbornly low inflation and lift growth. But the moves were considered by markets to be the bare minimum in the light of the bank’s previous signals.

One source with direct knowledge of the situation interpreted Draghi’s public stance ahead of the meeting as trying to pressure the Governing Council to take bigger action.

"Draghi raised expectations too high, on purpose, and attempted to paint the Governing Council into a corner," the source said. "This was problematic and he was criticised for this by several governors in private."

Unlike last year, when opponents of quantitative easing made their stance public before the decision, the hawks mostly worked behind the scenes.

Opponents worked to curtail proposals coming out of the ECB’s committees that prepared the decisions, ensuring that some of the more radical measures expected by market players never made it onto the table.

Markets also expected a 25 percent increase in monthly asset purchases and possibly even a deeper rate cut. More radical options under discussion included the purchase of corporate debt or a split deposit rate that would punish banks parking too much cash with the central bank, sources told Reuters earlier.

"What was in the end adopted was the set of options that could gather a comfortable majority. More exotic ones, obviously could not, and were hence not even proposed," another source said. "Sometimes discussions at the committees provide a clear enough picture."

In the weeks leading up to Governing Council meetings the ECB’s inner core of executive board members regularly sound out national central banks to gauge their positions and formulates proposals it knows will get a comfortably majority.

"It was better for Mario to have more or less a consensus than to push something that could backfire," another source said.

Draghi defended the package, arguing that it was meant to address inflation expectations not market predictions.

"There is no doubt that if we had to intensify the use of our instruments to ensure that we achieve our price stability mandate, we would," he said on Friday.

The smaller than expected move is seen by some as a disappointment for Draghi, who has established a track record for promising and delivering big, as he did with his July 2012 pledge to "do whatever it takes" to preserve the euro and pushing through bigger than expected QE earlier this year.

"Like the Fed earlier this year the ECB has now managed to confuse markets and the public. From now on, markets will treat hints dropped by ECB president Mario Draghi and some of his colleagues with much more scepticism than before," brokerage Berenberg said.

Although raising expectations too high was seen by some as a communications error, Draghi still managed to form a broad consensus and proved that he is not always guided by markets, as some critics have suggested, several sources said.

"So far Draghi was always seen as the perfect communicator. Maybe you can’t be perfect all the time," one of the sources said.

FED CONCERNS

Some council members were also concerned that too much easing by the ECB could force the U.S. Federal Reserve to delay its rate hike, which could increase market volatility as investors would need to reassess their Fed rate path forecasts.

"If we had over delivered, the euro could have gone down to parity and it would have been more difficult for (Fed Chair Janet) Yellen to defend an even stronger dollar. Now the Fed will be quite relaxed," one of the sources said.

The Fed is widely expected to raise interest rates for the first time in nearly a decade later this month but some rate setters have been concerned over the strength of the dollar, especially against the euro.

"There was a good argument for a smaller move so as to not influence the Fed and let them do what they needed to do," the source said.

The euro surged nearly 4 percent against the dollar after the ECB’s decision was announced on Thursday, a bigger rise than expected by the bank.

"We knew there would be a market reaction but it’s been bigger so far than we anticipated," one of the sources said.

Fresh economic forecasts by the bank's staff, which showed only a modest cut in the inflation outlook and an increase in some GDP projections, also made it tough to argue for a bigger easing, the sources said.

"Don’t forget in October everyone was worrying about China and the meltdown in emerging markets. Things have steadied in both cases," one of the sources said.

Several central bankers also argued that the ECB needed to hold back as governments in Germany, France, Italy and Austria were having to increase spending on refugees, security and defence.

"Up to now we had headwinds from fiscal policy. Now we have a tailwind from fiscal policy," a source said.

"We have kept some powder dry. Now if we need to, we can react," the person added.